It is frequently desirable to restrict the use of telephones, for example so as to avoid unauthorized toll charges. Apparatus for giving effect to this aim is known. Such apparatus in one form thereof includes counting means for counting the number of dial pulls. When these exceed a certain number, generally seven, simple logic means provides an output signal which serves to actuate line disconnect means. In another form to the apparatus, counting means is provided to count one or more dialed digits. Logic means is provided giving an output signal which serves to actuate line disconnect means when a dialed pulse or pulses correspond to predetermined prohibited numbers. Generally in this apparatus the prohibited numbers will comprise the numbers 0 or 1 as the first dialed digit, and 1 as the second dialed digit; the third digit may also comprise a prohibited number. In a variation of this form of apparatus, logic circuitry is programmed to accept specific numbers, generally three digit numbers indicative of local exchanges, and deny all others. Each of the above described forms of the apparatus may be considered to comprise input circuitry for receiving signals representing dialed digits, detector circuitry to recognize prohibited digits, and blocking circuitry responsive to the ddetector circuitry to restrict the communication.
In many commercial organizations where it is desirable to use a restriction system it may be desirable or even necessary to overcome or disable the system so that selected personnel are able to have complete and unrestricted access to any exchange and number they require. This has been recognized in the past. U. S. Pat. No. 3,873,781--NISSIM, dated Mar. 25, 1975 describes an arrangement where the hand set remains in the cradle while an "access" code is dialed to overcome the restriction. This required a special dial mechanism or switching mechanism at the telephone set. A somewhat similar solution is described in U.S. Pat. No. 4,099,033--MURRAY, dated July 4, 1978 where unauthorized use of a telephone is ensured by a restrictive system where authorized users are provided with a code to be dialed in on a special telephone set or on separate equipment attached to the telephone set. Again, there must be special equipment at the set. Other ways of providing access of unlimited dialing privileges (i.e. unrestricted calling privileges) to authorized users are by means of a coded card inserted into an accessory at the telephone set as described in U.S. Pat. No. 4,045,619--HARRINGTON, dated Aug. 30, 1977, and by means of a precise tone generator applied to the telephone mouth piece as described in U.S. Pat. No. 4,096,357--MOGTADER, dated June 20, 1978. All these require modified or auxiliary equipment at the telephone set.
It is therefore an object of this invention to provide a telephone restriction system having means for overcoming or disabling the restriction in response to an access code dialed into a standard telephone set in the system.
It is another object of the invention to provide a new and improved telephone restriction system that can be disabled using an access code.
It is yet another object of the invention to provide a telephone restriction system with means for disabling the restriction using a programmable access code at a standard telephone set.